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        <h2 id="说明-2022-05-05"><a class="markdownIt-Anchor" href="#说明-2022-05-05"></a> 说明 - 2022-05-05</h2>
<p>本篇博客为本人原创, 原发布于CSDN, 在搭建个人博客后使用爬虫批量爬取并挂到个人博客, 出于一些技术原因博客未能完全还原到初始版本(而且我懒得修改), 在观看体验上会有一些瑕疵 ,若有需求会发布重制版总结性新博客。发布时间统一定为1111年11月11日。钦此。</p>
<h2 id="p4408-noi2003-逃学的小孩"><a class="markdownIt-Anchor" href="#p4408-noi2003-逃学的小孩"></a> P4408 [NOI2003] 逃学的小孩</h2>
<p>​<br />
#include <iostream><br />
#include <cstdio><br />
#include <cstdlib><br />
#include <cstring><br />
#include <cmath><br />
#include <algorithm><br />
#include <string><br />
#include <queue><br />
#include <vector><br />
#include <stack><br />
#include <map><br />
#include <set><br />
typedef long long int LL;<br />
const int N = 2e5+5, M = -1, INF = 0x7fffffff;<br />
int n,m,u,v,pid,tid;<br />
LL w,plong,tlong;<br />
int idx;<br />
int head[N];<br />
LL disa[N],disb[N];<br />
struct Edge<br />
{<br />
int to,nxt;<br />
LL w;<br />
}edg[N&lt;&lt;1];<br />
void addEdge(int fr,int to,LL w)<br />
{<br />
edg[idx].to = to;<br />
edg[idx].nxt = head[fr];<br />
edg[idx].w = w;<br />
head[fr] = idx++;<br />
}<br />
void initial()<br />
{<br />
idx = 2;<br />
}<br />
void dfs(LL leng,int id,int efrom)<br />
{<br />
if(leng &gt; plong){<br />
plong = leng;<br />
pid = id;<br />
}<br />
for(int e=head[id]; e; e=edg[e].nxt){<br />
if((e^1) == efrom) continue;<br />
dfs(leng+edg[e].w,edg[e].to,e);<br />
}<br />
}<br />
void DFS(LL dis[],int x,int efrom,LL leng)<br />
{<br />
dis[x] = leng;<br />
for(int e=head[x]; e; e=edg[e].nxt){<br />
if((e^1) == efrom) continue;<br />
int y = edg[e].to;<br />
DFS(dis,y,e,leng+edg[e].w);<br />
}<br />
}<br />
int main()<br />
{<br />
initial();<br />
scanf(&quot;%d%d&quot;,&amp;n,&amp;m);<br />
for(int i=0; i&lt;m; i++) {<br />
scanf(&quot;%d%d%lld&quot;,&amp;u,&amp;v,&amp;w);<br />
addEdge(u,v,w);<br />
addEdge(v,u,w);<br />
}<br />
pid = 1, plong = 0;<br />
dfs(0,pid,0);<br />
tid = pid;<br />
pid = tid, plong = 0;<br />
dfs(0,pid,0);<br />
DFS(disa,tid,0,0);<br />
DFS(disb,pid,0,0);<br />
tlong = 0;<br />
for(int i=1; i&lt;=n; i++){<br />
tlong = std::max(tlong,std::min(disa[i],disb[i]));<br />
}<br />
printf(&quot;%lld&quot;,tlong+plong);<br />
return 0;<br />
}</p>

      
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